spect and pet for osteomyelitis imaging - up.ac.za · • in both subacute and chronic...

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SPECT AND PET FOR

OSTEOMYELITIS IMAGING

Christophe Van de Wiele, M.D., Ph.D.

University Hospital Ghent

Belgium

SPECT AND PET IN OSTEOMYELITIS

• Definition, prevalence and classification

• Pediatric versus Adult osteomyelitis

• Imaging in acute osteomyelitis

• Imaging in chronic osteomyelitis

– General

– Diabetic foot

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Osteomyelitis: Definition

• Infection of

– bone (osteo)

– and bone marrow (myelitis)

• Aetiology

– Mostly bacterial,

– Occasionally fungal

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Osteomyelitis

• Subdivided clinically into:

– Pediatric versus Adult

– Hematogenous vs. Direct spread

– Duration: acute , subacute chronic

– Special cases IVDA , Sickle cell

Prevalence of osteomyelitis

• Children 1/5000

• Sickle cell patients 3.6/1000

• Post puncture wound to foot 16/100

• Neonates 1/1000

• Post puncture wound to foot

in diabetics 30-40/100

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– General

– Diabetic foot

Pediatric Osteomyelitis

• >> Hematogenous spread – Involved micro-organisms:

• Staph Aureus,

• Streptococcus,

• H. Influenzae,

• Coliforms)

• >>long bones: tibia, humerus, femur.

• >>>acute – (tumor, rubor, calor, dolor, immobilization)

• << direct (Skin lesion extension) to bone– spina bifida, quad.

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Pediatric Osteomyelitis:

• Special cases

– Sickle cell disease:

• Osteomyelitis of the long bones

• Often due to salmonella sp.

– Teenagers:

• Osteomyelitis of the long bone and joint infections

• GC

• Non-anastomosing capillary

ends of nutrient arteries form

sharp loops under the

growth plates and enter

large venous sinusoids

where the blood flow is slow

and turbulent, trapping the

organisms

Why the long bones?

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Adult Osteomyelitis

• >> Direct extension of infection to the bone from a skin ulceration, leading cause of amputations

• >Direct inoculation to the bone from an open/contaminated fracture, or during ORIF, post-op TKA, THA

• >>>subacute and chronic– Localized pain, drainage, deformity, instability

• <<Hematogenous seeding from IVDA

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Adult Osteo. additional features:

• IVDA: Hematogenous seeding site more

likely to be spine or pelvis only

occasionally to the long bones

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Acute Osteo Sub-Acute Osteo Chronic Osteo

•Begins with marrow

edema, cellular

infiltration and vascular

engorgement

•May progress to

necrosis and abscess

formation

•Spread within the

intramedullary cavity �

extension through

cortex by Havers and

Volkman’s canals �

subperiosteal space �

periosteum � soft

tissues

•Rupture of joint space

� septic arthritis

• Occurs in abnormal

bone or after inadequate

antibiotics

•Localized pyogenic

process

•Commonly appears as a

well-defined osteolytic

metaphyseal lesion

(Brodie’s abscess) with a

sclerotic margin that

fades peripherally (fuzzy

sclerotic margin)

•S. aureus is most

common pathogen

• Occurs after inadequate tx or

in pts with altered immunity

•Distinguishing feature is

necrotic bone surrounded by

granulation tissue

•Interruption of blood supply

� necrosis � devitalized

bone fragments (sequestra)

•A thick sheath of new

periosteal bone can develop

around the sequestra

(involucrum)

•Fistula tract formation

•Sharp interface between

normal and diseased marrow






– General

– Diabetic foot

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FDG PET(-CT) IMAGING IN ACUTE OSTEOMYELITIS

• Diagnosis of acute osteomyelitis based

upon clinical history, clinical appearance,

biochemical and conventional imaging is

mostly straightforward

no need for complexe nuclear medicine

techniques






– General

– Diabetic foot

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Conventional Radiography• Modality of choice for initial evaluation

• Advantages– Inexpensive

– Exclude other conditions

– May help guide further work-up

• Disadvantages– Often normal for the first 10 to 21 days of infection

– Sensitivity: 43-75%

– Specificity: 75-83%

CT Imaging

• Advantages:– Best method to detect small foci of intraosseous gas,

areas of cortical erosion or destruction, tiny foreign

bodies, involucrum and sequestration formation

– Good for evaluation of chronic osteomyelitis: cortical

thickening, sclerosis, fistula draining

– Good for identifying abnormalities that must be fixed

at surgery (sequestra, involucra, fistula)

– Can be used to guide aspirations and bone biopsies

• Disadvantages– Sensitivity and specificity not clearly established

– Lower sensitivity than MRI

– Limited assessment of bony parts with metalic

implants due to beam hardening artifact

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Subacute MRI Findings

• Brodie’s abscess – (intraosseous abscess, internal wall covered by granulation

tissue)

16 y/o with Brodie’s abscess.

T1 weighted image of the

knee (A) demonstrates the

double line effect, a focal

area of low signal with

alternating bands of high and

low signal. Axial T2

weighted image of the

proximal tibia at the same

level (B) demonstrates a

region of high-intensity

surrounded by alternating

bands of low signal and high

signal.

�Subacute osteo is often confused with tumor (osteosarcoma, Ewing)

Chronic MRI Findings• In both subacute and chronic osteomyelitis, a

peripheral area of low-signal intensity (the rim sign) on all pulse sequences is visualized. Corresponds to fibrous change or reactive bones.

– Reported in 93% of patients with chronic osteomyelitis and in less than 1% of patients with acute.

• Usual appearance of high T2 signal in marrow may be absent. Instead, there are areas of devascularized fibrotic scaring which are low intensity signal onT1 and T2 images.

• Predominant bone sclerosis with cortical thickening

• Sinus tracts, sequestra, soft tissue abscesses

• Sharp interface between normal and abnormal marrow

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Sensitivity and Specificity of MRI in Osteomyelitis

*Adapted from Restrepo et al, 2003

Reference Sensitivity% Specificity% Location

Modic, 1986 96 92 Spine

Unger,1988 92 96 Multiple

Yuh, 1989 100 89 Foot

Wang, 1990 99 81 Foot

Erdman, 1991 98 75 Multiple

Zynamon,1991 100 78 Foot

Weinstein,1993 100 89 Multiple

Morrison, 1995 82 80 Foot

Mazur, 1995 97 92 Multiple

Morrison,1998 84-96 78-88 Foot

Haung, 1998 98 89 Hips/Pelvis

Nuclear Medicine Imaging

• Four types of studies may be used:– Bone Scan

– Gallium Scan

– White Blood Cell Scan

– FDG PET imaging

• General Advantages– Can image patients with prostheses without interference

– Easier for pediatric patients (pts usually don’t need

sedation)

– Multiple foci of disease can be demonstrated

– Sensitivity and Specificity similar to MRI

• General Disadvantages– Limited spatial resolution

– Less ability to delineate complex anatomy

– Circulatory compromise can interfere with study

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Bone Scan• 3-phase bone scan performed after injection of

methylene diphosphonate (MDP)

• Immediate, 15 minute and 3-4 hour images are

obtained.

• Abnormal findings for osteo include:

– Increased flow activity

– Blood pool activity

– Positive uptake on 3 hour images

• High sensitivity for osteomyelitis– Sensitivity 73 to 100%

• Specificity for osteo decreases when other conditions

are simultaneously present � recent trauma, surgery

or diabetes– Specificity: 73% to 79% but as low as 38% with complicating

conditions

Bone Scan Image

Patient with a history of puncture wound at the base of the thumb. Plain

radiograph (A) of the hand is normal. Three phase bone scan (B–D)

demonstrates increased flow of radiotracer to the soft tissues and increased

uptake in the bone consistent with osteomyelitis involving the base of the first

metacarpal bone.

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Gallium Scan

• Imaging preformed 24 to 48 hours after injection of Gallium

• Relatively high sensitivity– Sensitivity: 25% to 80%

• Specificity similar to bone scan– Occasional false positives from fractures, tumor

uptake

– Specificity: 67%

• Image quality may not be as good as the bone scan and it takes longer

• Marked excretion through the GI tract

White Blood Cell Scan• Indium –labeled WBC or HMPAO-labeled WBC

• Accumulation at sites of inflammation

• Compared to HMPAO, the Indium-labeled has:– Higher radiation dose to pt

– Takes 24 hours to perform

– Images with extensive noise

– Sensitivity of 90%, Specificity of 78%

• Compared to Indium, the HMPAO-labeled has:– Lower radiation dose to pt

– Same day study and result

– Better image quality

– Similar sensitivity and specificity

• Both types are superior to bone scan when imaging patients with complicating conditions

– Specificity increases to 80% to 90%

• Difficult to distinguish between acute, chronic or partially tx infection

Image

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Increased Specificity with WBC Scan

Compared to Bone Scan

Patient with a history of trauma and possible

osteomyelitis at the level of the right ankle. Bone

scan (A) demonstrates increased uptake in the

posterior calcaneus. White blood cell scan (B) is

normal and excludes the possibility of

osteomyelitis. The increased uptake on the bone

scan could be explained from prior trauma.

FDG PET(-CT) IMAGING

• First study– N= 22 pts

– Suspected chronic osteomyelitis

– FDG-PET • sens 100%, spec 87.5%, accuracy of 90.9%

– 2 false positives: 1 tibial non-union, 1 osteotomy

– Final diagnosis was made by surgical exploration or clinical follow-up during a 1-year period

• Second study:– FDG appears to normalize rapidly following traumatic or surgical

fractures as fibroblast predominate in normally healing bone

Zhuang et al, Clin Nuc MEd 2000, Exclusion of chronic osteomyelitis with 18F-FDG PET imaging

Zhuang et al, EJNMI 2003, Rapid normalization of osseous FDG-uptake following traumatic or

surgical fractures

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FDG PET(-CT) IMAGING IN CHRONIC OSTEOMYELITIS

Fluorine-18 fluorodeoxyglucose-positron emission tomography: a highly accurate imaging modality for the diagnosis of chronic musculoskeletal infections

• Prospectively

• n = 60: 33 central skeleton, 27 peripheral skeleton; 35 pts had surgery in past 2 years

• histopathological studies or microbiological culture (18 patients) or on clinical findings after at least six months of follow-up (42 patients)

• Results:

– 25 pts infection, correctly identified

– 35 pts no infection

– 4 false false-positive findings;

• in 2: surgery < 6 months prior

to the study

• Conclusions:

– 18F- FDG-PET is highly accurate as a single technique for the evaluation of chronic musculoskeletal infections.

– Especially valuable in the evaluation of the central skeleton, where white blood-cell scans are less useful.

– Simplicity and high degree of accuracy: the potential to become a standard technique for the diagnosis of chronic musculoskeletal infections.

De Winter et al, J Bone Joint Surg; 2001, 83-A: 651-660

PET Sensi Speci Accuracy

Whole group 100% 88% 93%Central skeleton 100% 90% 94%

Peripheral

skeleton100% 86% 93%


Termaat et al, Bone Joint Surg Am 2005;87:2464-71 The accuracy of diagnostic imaging for the

assessment of chronic osteomyelitis: systematic review and meta-analysis

Pooled

sensi

CI Pooled

speci

CI

PET 96% 88-99 91% 81-95

Bone

scintigraphy82% 70-89 25% 16-36

Leuko

scintigraphy61%Perif 84%-axial 21%

77%Perif 80%-axial 60%

63-87

Bone and

leukocyte scinti78% 72-83 84% 75-90

MRI 84% 69-92 60%

Conclusions:

1. FDG-PET has the highest diagnostic accuracy for confirming or excluding the diagnosis of chronic

osteomyelitis.

2. Leukocyte scintigraphy has an appropriate diagnostic accuracy in the peripheral skeleton, but FDG-PET is

superior for detecting chronic osteomyelitis in the axial skelet.

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• Conclusions

– High sensitivity and specificity values for chronic osteomyelitis with FDG-PET

– Negative FDG-PET : excludes presence of the disorder






– General

– Diabetic foot

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DIABETIC FOOT

• Early detection leads to treatment (antibiotics) and decreases amputation rate

• Bone marrow edema and contrast enhancement on MRI are – not specific for osteomyelitis

– Occur in several other non-infectious diseases (stress fractures, necrosis and neuropathy)

• Bone biopsy: gold standard, risk of iatrogeneous infection!

• Radionuclide study of choice: labelled leucocyte imaging: accuracy 80%, less performing for the midfoot: due to marrow proliferation in Charcot joints: add colloid!!

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FDG PET(-CT) IMAGING IN DIABETIC FOOT

• Keidar et al, The diabetic foot: intial experience with 18F-FDG PET/CT (J N Med 2005; 46:444-9)

– FDG PET highly accurate in differentiation between osteomyelitis and soft-tissue infection

– 1 out of 18 sites false positive due to osteoarthropathy misinterpreted as osteomyelitis

– FDG PET/CT can be used for diagnosis of diabetes-related infection

• Schwegler et al, Unsuspected osteomyelitis is frequent in persistent diabetic foot ulcer and better diagnosed by MRI than by 18F-FDG PET or 99m Tc-MOAB (Int Med 2008;263:99-106)MRI (6/7) more sensitive than FDG-PET (2/7) for diagnosing diabetic pedal osteomyelitis

– N = 20 pts, 7 had histopathological proof of osteomyelitis

– MRI correct in all cases

– Only if MRI is inconclusive, conventional radionuclide imaging or FDG-PET/CT might help in the diagnosis of osteomyelitis

FDG PET(-CT) IMAGING IN DIABETIC FOOT

Nuclear medicine and diabetic foot infections

• Bone scan as screening test or localization

• Labeled leukocyte imaging– Sensi range: 72%-100%

– Speci range: 67%-98%

– Accuracy 99mTc or 111 In: similar

• SPECT-CT: to be investigated, probably useful in mid and hind foot

• FDG-PET and PET/CT: limited results and inconclusive

Palestro and Love, Semin Nucl Med. 2009 Jan;39(1):52-65

spect and pet for osteomyelitis imaging - up.ac.za · • in both subacute and chronic...

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